Conventionally smoke detectors have been known in which a battery, most usually a rectangular 9V battery (such as Eveready 216, 522 or 1222 or Duracell MN1604) is used to supply current to sound an alarm when activated by an ionisation chamber. Batteries are typically used for convenience of installation and relative economy. Using batteries obviates the need to connect to an external power supply, and batteries may be readily replaced when flat.
However, an improved smoke detector is envisaged wherein the smoke detector includes a transmitter. This is a highly desirable feature as the transmitted signal may be received by a nearby security system which can raise an alarm (e.g. through the conventional pubic switched telephone network). This is particularly useful in situations in which the premises are unattended, or if the audio alarm is otherwise unlikely to be heard, such as during the night, or at a retirement home.
At present it is only known to achieve this functionality by replacing the conventional smoke detector with a purpose-built smoke detector which specifically incorporates these features. However, the applicant has conceived that it is possible to retrofit existing conventional smoke detectors with a composite battery-transmitter according to an embodiment of the present invention. This modification is particularly elegant as it does not change the internal space of the smoke detector which might otherwise interfere with the smoke-detecting ability of the ionisation chamber. For this reason it substantially conforms in this respect with the anticipated Australian Standard for wireless smoke detectors. It is particularly desirable to recycle existing conventional smoke detectors rather than merely replacing them. This is because conventional smoke detectors contain radioactive materials in the ionisation chamber. Accordingly they should not be dismantled, destroyed or disposed of by untrained people. Thus recycling of smoke detectors obviates disposal problems while being particularly convenient.